LTE-Advanced systems use Orthogonal Frequency Division Multiple Access (OFDMA) access mode. The interference among multiple users within the same cell can be avoided since users' information is carried on orthogonal different sub-carriers. But OFDMA access method itself does not have the ability to suppress inter-cell interference, thus the adjacent cell interference, i.e., inter-cell interference is the main aspect affecting the performance of the LTE-Advanced system. At the same time, in order to achieve higher spectrum efficiency, broadband mobile communication systems will be deployed with frequency reuse factor close to one. In a cellular system with networking at the same frequency, cell edge users will be interfered easier from adjacent cell, such interference severely limits cell edge user's service quality and throughput.
For example, as illustrated in FIG. 1, the antenna of mobile terminal 1's serving Node B is antenna 1, the antenna of mobile terminal 2's serving Node B is antenna 2, and the antenna of mobile terminal 3's serving Node B is antenna 3. Assume mobile terminals 1, 2 and 3 transmit signals respectively to the antennas 1, 2 and 3 at the same time and frequency (e.g., a frequency point A). Antenna l's received signal at frequency point A includes the desired signal of mobile terminal 1 and the interference signals of mobile terminal 2 and mobile terminal 3, that is, the signal received by antenna 1 at frequency point A is a mixture of the signal transmitted from the mobile terminals 1, 2 and 3. Similarly, the interference signals of mobile terminal 1 and mobile terminal 3 are received by antenna 2 at the frequency point A in addition to the useful signal of mobile terminal 2, and the interference signals of mobile terminal 1 and mobile terminal 2 are received by antenna 3 at the frequency point A in addition to the useful signal of mobile terminal 3. That is, all the signals transmitted from mobile terminal 1, mobile terminal 2 and mobile terminal 3 can be received by antenna 1, antenna 2 and antenna 3.
On a downlink channel, mobile terminal 1 receives signals transmitted respectively from antenna 2 and antenna 3 to mobile terminals 2 and 3 in addition to a useful signal of antenna 1; Similarly, mobile terminal 2 receives signals transmitted respectively from antenna 1 and antenna 3 to mobile terminals 1 and 3 in addition to the useful signal of antenna 2, and mobile terminal 3 receives signals transmitted respectively from antenna 1 and antenna 2 to mobile terminals 1 and 2 in addition to the useful signal of antenna 3. That is, all the signals transmitted from antenna 1, antenna 2 and antenna 3 at the frequency point A can be received by mobile terminal 1, mobile terminal 2 and mobile terminal 3.
In order to alleviate such inter-cell signal interference, in the prior art, a cooperative set of antennas is consisted of antenna 1, antenna 2 and antenna 3 (as illustrated in FIG. 2), and a signal joint processing system performs a cooperative process on the signals received by the cooperative set of antennas from mobile terminals 1, 2 and 3 or transmitted by the cooperative set of antennas to the mobile terminals 1, 2 and 3 to improve a ratio of correctly detecting the signals of the mobile terminals by the antennas and a ratio of correct reception at the mobile terminals of the signals transmitted from the antennas.
In the prior art, the signal joint processing system of the cooperative set of antennas acquires information on channels between the respective antennas in the cooperative set of antennas and the mobile terminals (the channel information reflects qualities of the channels of communication between the antennas and the mobile terminals) and suppresses the interference signals of the mobile terminals in adjacent cells from the received signals through the technique of Multiple Input Multiple Output, MIMO.
The signal joint processing system acquires the signals received by antennas 1, 2 and 3 at the frequency point A and the information of the channels between antennas 1, 2 and 3 and mobile terminals 1, 2 and 3. The signal joint processing system suppresses the interference signals of the mobile terminals in the adjacent cells, by processing the received signals through MIMO, according to the acquired signals and channel information. So the system can detect the signals actually transmitted from mobile terminals 1, 2 and 3 (for example, the signals transmitted actually from the mobile terminals can be estimated in the following set 1 of equations):
                    {                                                                                                  A                    ⁢                                                                                  ⁢                    1                    ×                    X                                    +                                      B                    ⁢                                                                                  ⁢                    1                    ×                    Y                                    +                                      C                    ⁢                                                                                  ⁢                    1                    ×                    Z                                    +                                      n                    ⁢                                                                                  ⁢                    1                                                  =                                  P                  ⁢                                                                          ⁢                  1                                                                                                                                              A                    ⁢                                                                                  ⁢                    2                    ×                    X                                    +                                      B                    ⁢                                                                                  ⁢                    2                    ×                    Y                                    +                                      C                    ⁢                                                                                  ⁢                    2                    ×                    Z                                    +                                      n                    ⁢                                                                                  ⁢                    2                                                  =                                  P                  ⁢                                                                          ⁢                  2                                                                                                                                              A                    ⁢                                                                                  ⁢                    3                    ×                    X                                    +                                      B                    ⁢                                                                                  ⁢                    3                    ×                    Y                                    +                                      C                    ⁢                                                                                  ⁢                    3                    ×                    Z                                    +                                      n                    ⁢                                                                                  ⁢                    3                                                  =                                  P                  ⁢                                                                          ⁢                  3                                                                                        (        1        )            
Where P1, P2 and P3 represent the signals received by the antennas 1, 2 and 3 at the frequency point A respectively; A1, B1 and C1 represent the information on the channels between antenna 1 and the mobile terminals 1, 2 and 3 respectively; A2, B2 and C2 represent the information on the channels between antenna 2 and the mobile terminals 1, 2 and 3 respectively; A3, B3 and C3 represent the information on the channels between antenna 3 and the mobile terminals 1, 2 and 3 respectively; and n1, n2 and n3 represent noise and the interference signals of the other cells received by the antennas 1, 2 and 3 respectively; and the signals X, Y and Z transmitted actually from the mobile terminals 1, 2 and 3 can be estimated in the foregoing set 1 of equations.
Furthermore, a cooperative process on the signals transmitted to the mobile terminals is performed by the antennas in the cooperative set of antennas in order to improve the ratio of correct reception at the mobile terminals of the signals transmitted from the antennas when the signals are transmitted to the mobile terminals.
The signal joint processing system acquires data information to be transmitted to the mobile terminals 1, 2 and 3 and the information on the channels between the antennas 1, 2 and 3 and the mobile terminals 1, 2 and 3. According to the acquired data information and the channel information, the signal joint processing system weights the data information to be transmitted to the mobile terminals 1, 2 and 3 by using a beam forming algorithm to obtain transmission signals, which in turn are transmitted by the antennas 1, 2 and 3 at the frequency point A (for example, the signals transmitted by the antennas 1, 2 and 3 at the frequency point A can be derived in the following set 2 of equations):
                    {                                                                                                  A                    ⁢                                                                                  ⁢                    2                    ×                    R                    ⁢                                                                                  ⁢                    1                    ×                    X                                    +                                      B                    ⁢                                                                                  ⁢                    2                    ×                    R                    ⁢                                                                                  ⁢                    2                    ×                    X                                    +                                      C                    ⁢                                                                                  ⁢                    2                    ×                    R                    ⁢                                                                                  ⁢                    3                    ×                    X                                                  =                0                                                                                                                              A                    ⁢                                                                                  ⁢                    3                    ×                    R                    ⁢                                                                                  ⁢                    1                    ×                    X                                    +                                      B                    ⁢                                                                                  ⁢                    3                    ×                    R                    ⁢                                                                                  ⁢                    2                    ×                    X                                    +                                      C                    ⁢                                                                                  ⁢                    3                    ×                    R                    ⁢                                                                                  ⁢                    3                    ×                    X                                                  =                0                                                                        (        2        )            
Where A1, B1 and C1 represent the information on the channels between the mobile 1 and the antennas 1, 2 and 3 respectively; A2, B2 and C2 represent the information on the channels between the mobile 2 and the antennas 1, 2 and 3 respectively; A3, B3 and C3 represent the information on the channels between the mobile 3 and the antennas 1, 2 and 3 respectively; and the foregoing equations can be solved into multiple sets of R1, R2 and R3, one of which is selected as weights for the data information to be transmitted respectively from antennas 1, 2 and 3 to mobile terminal 1. Similarly, weights R1′, R2′ and R3′ for the data information to be transmitted respectively from the antennas 1, 2 and 3 to mobile terminal 2 and weights R1″, R2″ and R3″ for the data information to be transmitted respectively from the antennas 1, 2 and 3 to mobile terminal 3 can be calculated. Thus, the signal transmitted from antenna 1 at the frequency point A is: R1×X+R1′×Y+R1″×Z; the signal transmitted from antenna 2 at the frequency point A is: R2×X+R2′×Y+R2″×Z; and the signal transmitted from antenna 3 at the frequency point A is: R3×X+R3′×Y+R3″×Z, where X, Y and Z represent the data information to be transmitted to the mobile terminals 1, 2 and 3 respectively.
However, in the scenario illustrated in FIG. 3a, mobile terminal 2 receives a stronger interference signal from antenna 4 than from antenna 1. Therefore, there is an imperfect effect of suppressing the signal interference at mobile terminals at the edge of some cells (e.g., mobile terminal 2 in FIG. 3a) although the ratio of correct signal reception at mobile terminals at the edge of some other cells (e.g., mobile terminals 1 and 3 in FIG. 3a) can be improved by using the foregoing method with a cooperative set of antennas in the prior art; or in the scenario as illustrated in FIG. 3b, most of the interference signals in the signal transmitted from mobile terminal 2 and received by antenna 2 is from the mobile terminal 4 and mobile terminal 3 instead of mobile terminal 1 participating in calculation of signal interference in the prior art, therefore there is a limited effect of suppressing interference to the signal received and transmitted at mobile terminal 2 in the method of the prior art in the scenario as illustrated in FIG. 3b. 
In conclusion, the method to suppress inter-cell signal interference in the prior art cannot always suppress interference to a signal communicated between a mobile terminal and an antenna in various practical situations effectively so that a quality of communication between the antenna of a Node B and some mobile terminals at the edge of a cell cannot be ensured at all time; and alike the existing method for suppressing inter-cell signal interference cannot always suppress interference to a signal communicated between a mobile terminal and a Node B in various practical situations effectively so that the quality of communication between the Node B and some mobile terminals at the edge of a cell can not be ensured at all time.